<template>
  <div>
    <div class="goods">
      <div class="menu-wrapper">
        <ul>
          <!--current-->
          <li class="menu-item" v-for="(good, index) in goods" :key="index" 
          :class="{current: index===currentIndex}" @click="clickMenuItem(index)">
            <span class="text bottom-border-1px">
              <img class="icon" :src="good.icon" v-if="good.icon">
              {{good.name}}
            </span>
          </li>
        </ul>
      </div>

      <div class="foods-wrapper">
        <ul ref="foodsUl">
          <li class="food-list-hook" v-for="(good, index) in goods" :key="index">
            <h1 class="title">{{good.name}}</h1>
            <ul>
              <li class="food-item bottom-border-1px" v-for="(food, index) in good.foods" 
              :key="index" @click="showFood(food)">
                <div class="icon">
                  <img width="57" height="57" :src="food.icon">
                </div>
                <div class="content">
                  <h2 class="name">{{food.name}}</h2>
                  <p class="desc">{{food.description}}</p>
                  <div class="extra">
                    <span class="count">月售{{food.sellCount}}份</span>
                    <span>好评率{{food.rating}}%</span>
                  </div>
                  <div class="price">
                    <span class="now">￥{{food.price}}</span>
                    <span class="old" v-if="food.oldPrice">￥{{food.oldPrice}}</span>
                  </div>
                  <div class="cartcontrol-wrapper">
                    <cartControl :food="food"></cartControl>
                  </div>
                </div>
              </li>
            </ul>
          </li>
        </ul>
      </div>
      <ShopCart></ShopCart>
    </div>
    <Food :food="food" ref="food"></Food>
  </div>
</template>

<script>
import BScroll from 'better-scroll'
import cartControl from '../../../components/cartControl/cartControl.vue';
import Food from '../../../components/Food/Food.vue'
import ShopCart from '../../../components/ShopCart/ShopCart.vue'
import {mapState} from 'vuex'

export default {
    data () {
      return {
        scrollY: 0,  //右侧滑动的Y轴坐标(滑动过程实时变化)
        tops: [],  //所有右侧分类li的top组成的数组  (列表第一次显示后就不在变化)
        food: {}, // 需要显示的Food
      }
    },
    mounted () {
        //这是异步获取数据
        this.$store.dispatch('getShopGoods', () => { //数据更新完成后更新
          this.$nextTick( () => {
            this._initScroll(),
            this._initTops()
          })
        }) 
    },
    computed: {
        ...mapState(['goods']),

        // 计算得到当前分类的下标
        currentIndex () { // 初始时执行和数据发生变化时执行
          // 得到条件数据
          const {scrollY, tops} = this
          // 根据条件产生一个结果
          const index = tops.findIndex((top, index) => {
            // scrollY>=当前top && scrollY<=下一个top
            return scrollY >= top && scrollY < tops[index+1]
          })
          //返回结果
          return index
        }
    },
    methods: {
      // 初始化滚动条 (加下划线与事件相关的回调函数区分)
      _initScroll () {
        // 列表显示之后创建
        new BScroll('.menu-wrapper', {
          click: true
        })
        this.foodsScroll = new BScroll('.foods-wrapper', {
          probeType: 3,  // 手指离开后不会触发(惯性滑动不会触发)
          click: true
        })  

        // 给右侧列表绑定scroll监听
        this.foodsScroll.on('scroll', ({x, y}) => {
          //console.log(x, y)
          this.scrollY = Math.abs(y) //返回数的绝对值
        })

        // 给右侧列表绑定scroll结束的监听
        this.foodsScroll.on('scrollEnd', ({x, y}) => {
          //console.log(x, y)
          this.scrollY = Math.abs(y) //返回数的绝对值
        })
      },
      _initTops () {
        //1. 初始化tops
        const tops = []
        let top = 0
        tops.push(top)
        //2. 收集

        //得到所有分类的li
        //const lis = this.$refs.foodsUl.children
        const lis = this.$refs.foodsUl.getElementsByClassName('food-list-hook')
        //将伪数组变成真数组
        Array.prototype.slice.call(lis).forEach(li => {
          top += li.clientHeight   //clientHeight元素内部的高度
          tops.push(top)
        });

        //3. 更新数据
        this.tops = tops
        //console.log(tops)
      },

      clickMenuItem (index) {
        // console.log(index)
        // 使右侧列表滑动到对应的位置
        // 得到目标位置的scrollY
        const scrollY = this.tops[index]
        // 立即更新scrollY(更新点击的分类项)
        this.scrollY = scrollY
        // 平滑滚动右侧列表
        this.foodsScroll.scrollTo(0, -scrollY, 300)
      },

      //显示点击的food
      showFood (food) {
        //设置food
        this.food = food
        //显示food组件(在父组件中调用子组件对象的方法)  用ref获取整个food对象
        this.$refs.food.toggleShow()
      }
    },
    components: {
      cartControl,
      Food,
      ShopCart
    }
}
</script>

<style lang="stylus" scoped>
 @import "../../../common/stylus/mixins.styl"
  .goods
    display: flex
    position: absolute
    top: 195px
    bottom: 46px
    width: 100%
    background: #fff;
    overflow: hidden
    .menu-wrapper
      flex: 0 0 80px
      width: 80px
      background: #f3f5f7
      .menu-item
        display: table
        height: 54px
        width: 56px
        padding: 0 12px
        line-height: 14px
        &.current
          position: relative
          z-index: 10
          margin-top: -1px
          background: #fff
          color: $green
          font-weight: 700
          .text
            border-none()
        .icon
          display: inline-block
          vertical-align: top
          width: 12px
          height: 12px
          margin-right: 2px
          background-size: 12px 12px
          background-repeat: no-repeat
        .text
          display: table-cell
          width: 56px
          vertical-align: middle
          bottom-border-1px(rgba(7, 17, 27, 0.1))
          font-size: 12px
    .foods-wrapper
      flex: 1
      .title
        padding-left: 14px
        height: 26px
        line-height: 26px
        border-left: 2px solid #d9dde1
        font-size: 12px
        color: rgb(147, 153, 159)
        background: #f3f5f7
      .food-item
        display: flex
        margin: 18px
        padding-bottom: 18px
        bottom-border-1px(rgba(7, 17, 27, 0.1))
        &:last-child
          border-none()
          margin-bottom: 0
        .icon
          flex: 0 0 57px
          margin-right: 10px
        .content
          flex: 1
          .name
            margin: 2px 0 8px 0
            height: 14px
            line-height: 14px
            font-size: 14px
            color: rgb(7, 17, 27)
          .desc, .extra
            line-height: 10px
            font-size: 10px
            color: rgb(147, 153, 159)
          .desc
            line-height: 12px
            margin-bottom: 8px
          .extra
            .count
              margin-right: 12px
          .price
            font-weight: 700
            line-height: 24px
            .now
              margin-right: 8px
              font-size: 14px
              color: rgb(240, 20, 20)
            .old
              text-decoration: line-through
              font-size: 10px
              color: rgb(147, 153, 159)
          .cartcontrol-wrapper
            position: absolute
            right: 0
            bottom: 12px
</style>